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Transcript
C3 Journey through Time
LO: to explain how Britain came into existence
as continents, how different climates Britain has
experienced and magnetic clues that geologists
use to track continents
Earth’s outer layer is made of tectonic plates, these plates
move because of very slow convection currents in the
underlying solid mantle.
Movements of the tectonic plates cause oceans to open
up slowly between continents in some parts of the
world. Plate movements bring continents together with
great force, creating mountain ranges. Major volcanic
eruptions and earthquakes happen at plate
boundaries.
To confirm this scientists used magnetic
particles in the rock to track the position
of north and south of the Equator.
Volcanic lava and sediments contain
mineral magnetite.
The mineral gets its name from
magnetic properties of its crystal.
Magnetite can be magnetised in a
fixed direction once the rock has
cooled enough.
The magnetisation line up in the direction of the Earth’s
magnetic field at the time. Near the Equator, the
magnetisation lies horizontally, nearer to the Poles, the
magnetisation is at an angle to the horizontal.
By measuring the angle at which crystals are magnetised
in rocks, scientists can work out the latitude at which the
rock was originally formed.
The evidence supported continental drift and
development of the theory of plate tectonics.
1)
What causes continents to move over the
surface of the Earth?
2)
Do the observations of magnetic minerals
made by the scientists at Imperial College
support or conflict with the theory of plate
tectonics?
3)
Suggest evidence that geologists might look
for to test the theory that the northern and
southern parts of Britain were once on
different continents.
Review Learning:
LO: to explain how Britain came
into existence as continents, how
different climates Britain has
experienced and magnetic clues
that geologists use to track
continents
Moving rocks
7th June
Aim
• To describe why different rocks provide evidence for plate
tectonics
Starter
Use the picture and
labels provided to join
up the correct name
and part of the
Earth’s structure.
Once you have completed the task
above, write a little bit about each
part.
Continental drift
Ring of fire
Plates move in a specific direction....
Which 3
different ways
is it possible for
the plates to
move...with
respect to each
other??
Look at the
arrows.
Constructive boundary
The recent volcanic ash
cloud in Iceland ruined
flights for months...
Destructive boundary
The Nazca plate is moving
beneath the South American
plate. This pushes the
continental crust upwards.
Conservative boundary
Pacific plate meets
the North American
plate
Modelling sedimentary rock
BEAKER
This beaker is similar to the one Mr
Johnson is holding.
WATER
SAND
Using your common sense, discuss
and agree on suitable answers to the
questions above.
Write your answers in your books
Swamp areas
Origin of rock
Produces chalk (calcium
carbonate) which is a
compound found in bones
and shells.
Desert areas
Produces coal (mainly
carbon). Plant matter can be
changed into coal if the
conditions prevent it rotting.
Warm oceans
Produces red sandstone
when deposited via
wind and rain.
Compasses...what’s the point?
Which direction does your compass
point?
Why do all compasses point this way?
THIS HAS SOMETHING TO DO WITH THE
EARTH AND WHAT THE COMPASS IS
MADE OF
Is there any way of changing the was a
compass points?
USE THE MAGNET PROVIDED TO SHOW
WHAT HAPPENS WHEN YOU GET NEAR TO
IT
Are rocks magnetic??
Minerals in Britain
LO: to explain what geologists can learn by
studying can learn by studying rocks and the
origins of some of the rocks in Britain
Geologists can use the Earth’s surface to explain the
history. Sedimentary rocks contains grains and these
can be compared and geologists can tell how the rock
was made by the shape and size.
Fossils of plants and animals
can tell us about the life on
the planet at different
geological time.
A chemical industry based on chlorine grew by the River
Mersey because underground salt deposits, coal mines
and lime stone quarries were nearby. These provided the
raw material for making chlorine. The salt, coal and
limestone formed at different times and different
climates of Britain’s long geological history.
Review Learning:
LO: to explain what geologists
can learn by studying can learn
by studying rocks and the origins
of some of the rocks in Britain
Chemicals from Salt
LO: to explain how alkalis were first
manufactured on a large scale, why this was
such a polluting process and how Parliament
began to regulate the chemical industry
During the 1700s there was a huge demand for alkalis.
In 1791, Nicolas Leblanc invented a new
process that used chalk or limestone
(calcium carbonate), salt (sodium
chloride) and coal to make the alkali
sodium carboante.
In England , Widnes and Runcorn, became the areas
where this was produced due to the salt.
The process was highly polluting
as solid waste was produced. It
also released hydrogen chloride
gas into the air.
This acidic gas devastated the land around and the
solid waste dumped outside the factory slowly
gave off a steady stream of toxic hydrogen
sulphide gas.
During the 1800s, industries grew and the British public
demanded action from Government to control the
pollution.
Pollution became so bad that in 1863, Parliament
passed the first of the Alkali Acts. This Act set up an
Alkali Inspectorate who travelled the country to check
that at least 95% of acid fumes were removed from
the chimneys of chemical factories.
They would dissolve the hydrogen chloride in water,
this was released into water systems and it killed all
the life .
In 1874, Henry Deacon invented a way to
use the gas. He found that it was
possible to oxidise hydrogen chloride to
chlorine which can then be used to
bleach (bleach paper and textiles).
He mixed hydrogen chloride with oxygen and let the
two gases flow over a hot crystal. The products
produced were chlorine and gas.
Review Learning:
LO: to explain how alkalis were
first manufactured on a large
scale, why this was such a
polluting process and how
Parliament began to regulate the
chemical industry
Alkalis
LO: to explain the used of alkalis, where alkalis
used come from and the reaction of
neutralisation of acids with alkalis
These can be used for;
• neutralising acid soils
• convert fats and oils to soap
• making glass
• make chemicals that bind natural dyes to cloth
Alum is used for dyeing cloth, it
helps the dyes to cling fast to the
cloth, so that the colours did not
fade too quickly during washing.
It was made on the north-east coast of Britain, where
rock from the cliffs is rich in aluminium compounds. The
rock was roasted in open-air fires for many months. Then
they tipped the burnt rock into pits of water and stirred
the mixture with long wooden poles.
The rock is then settled, the solution of soluble
chemicals into lead pans. There they boiled the liquid
to get rid of the water and added an alkali to
neutralise acids in the solutions. The solution was
cooled in wooden casks. Crystals formed and they
would be crushed for sale.
Potash was one of the alkali
used, this is ash of burnt
wood. Others were ammonia
from stale urine.
• alkalis are soluble in water
• when dissolved they raise the pH of water above 7
• they neutralise acids
• two very corrosive alkalis are sodium hydroxide and
potassium hydroxides
• when they neutralise with acids, salt and water are
produced
Acid
+
Alkali
Salt
+
Water
1) At which stages of the manufacture of alum were the
following process involved? Which processes involved
chemical reactions to make new chemicals?
a) Oxidation
b) dissolving
c) Evaporation
d) Neutralisation
e) Crystallisation
2) Stale urine contains 2g of ammonia in 100 cm3 of the
liquid. The daily output of a person is about 1500 cm3
of urine.
a) Estimate the mass of ammonia, in tonnes, that could
be obtained per person per year (1 tonne = 1000 kg =
100g)
b) 3.75 tonnes of ammonia is needed to make 100 tonnes
of alum. Estimate the number of people needed to
supply the urine for an alum works producing 100
tonnes of alum per year.
Review Learning:
LO: to explain the used of alkalis,
where alkalis used come from
and the reaction of
neutralisation of acids with
alkalis
Ashes of
seaweed
and lime
were mixed
with sand
to make
glass.
Plant dyes (alkali) mixed with
alum, made the colour stick
pH of soil can be changed
by adding alkali (lime)
Ash from burnt plants was used
as an alkali source... So was urine
from people’s homes
Making lime
The lime we use to neutralise soil can be made
using calcium carbonate.
If we heat up calcium carbonate (CaCO3) in a boiling
tube, it decomposes (which means no chemicals
react with it, just heat turns it into new products).
In this reaction, lime (chemical name is calcium
oxide, or CaO) is produced and a gas is given off.
To do:
1) Write a word equation for this
decomposition reaction. (You’ll need to have
a guess at the name for the gas given off)
2) Write a balanced symbol equation for this
reaction.
Protecting Health and Environment
LO: to be able to explain why there is a need to
check on the safety of a very large number of
chemicals, the European Union’s programme for
testing and the problem of persistent harmful
chemicals
Flammable
Toxic
Explosive
Corrosive
Harmful (h) or Irritant (i)
Oxidising
Dangerous to the Environment
World Wide Fund for Nature (WWF) and Greenpeace
are fearful of synthetic chemicals. The campaigners
have highlighted evidence suggesting that chemicals,
such as those found in plastics and pesticides, may
cause cancer, or lead to defects in new-born babies.
Scientists who study toxic chemicals agree that some
commonly used synthetic chemicals can be harmful in
large doses, but in concentrations found in bodies.
In 2007, the EU introduced the
REACH system to collect
information about the hazards of
chemicals and to assess the risks.
REACH switches most of the responsibility for control
and safety of chemicals from the authorities to the
companies that make them, or use them. Now industry
has to manage the risks of chemicals for human health
and tee environment.
There are some synthetic chemicals that do not break
down in the environment for a very long time. This
means they can spread widely around the world in air
and water. They build up in the fatty tissues of animals.
This set of chemicals is sometimes called the ‘dirty
dozen’. They are;
• eight pesticides (DDT and DDE)
• two types of compounds used in industry (PCBs)
• two by-products of industrial activity (dioxins)
The ‘dirty dozen’ are classified as persistent organic
pollutants (POPs). Many of the compounds contain
chlorine.
They are a problem for the Arctic, where traditional
diets are often high in fat. POPs tend to accumulate in
fatty tissue of animals.
At a Convention in Stockholm (2001) it was agreed to
deal with POPs. It was effective in 2004 and 150
countries have agreed to outlaw the ‘dirty dozen’.
Suggest reasons why Stockholm convention
allows the use of the insecticide DDT to
control mosquitoes in parts of the world
where malaria so a serious problem.
Review Learning:
LO: to be able to explain why
there is a need to check on the
safety of a very large number of
chemicals, the European Union’s
programme for testing and the
problem of persistent harmful
chemicals
Benefits and Risks of Plasticisers
LO: to be able to explain the chemical used to
plasticise PVC and to be able to explain the risks
of PVC and how they are regulated
Toymakers like to use PVC
because it very versatile:
• can be rigid or flexible
• mixed with pigments to give bright colours
• stands to rough play
• easy to keep clean
Plasticisers are chemicals that make PVC soft and
flexible. The most common plasticisers for PVC are
phthalates.
They are made of small molecules, which can escape
from the plastic and dissolve in liquids that are in contact
with it. They can also leach out of the plastic used to
make blood bags or intravenous drips and so enter
patient’s bodies.
The EU has restricted two common phthalate plasticisers
to toys that cannot be placed in the mouth. A third DEHP
has been completely banned.
PVC with DEHP was used in medical
devices. Though it would leach into
liquids. There are alternatives but they
are expensive.
Why does it makes sense for regulators to ban the
use of the DEHP in toys, but only to issue warnings
and advice about the use of medical equipment
made with PVC softened with the same plasticiser?
Review Learning:
LO: to be able to explain the
chemical used to plasticise PVC
and to be able to explain the
risks of PVC and how they are
regulated
Life Cycle Assessment
LO: to be able to explain what the life cycle
assessment is in terms of the product and the
impact the product has
The life of each of these products has four distinct phases;
1. The materials are made from natural raw
materials
2. manufacturers make products from the materials
3. people use them
4. people throw them away
Nan’s TV
Manufacturers can assess what happens to he materials in
their products. This LCA is part of legislation to protect the
environment.
The aim is to slow the rate at which we use up natural
resources that are not renewable. At each stage energy is
used.
An LCA involves collecting data about each stage in the life
of the product. It includes the use of materials/water,
energy inputs and outputs, and environmental impact.
Plastic Frame
Wooden Frame
Review Learning:
LO: to be able to explain what
the life cycle assessment is in
terms of the product and the
impact the product has